


Into the Breach

by Dirtykinkylove



Series: Infidelity Kink [2]
Category: Teen Wolf (TV)
Genre: Age Difference, Alternate Universe - No Werewolves, Always Female Stiles Stilinski, Dubious Morality, F/M, Infidelity, M/M
Language: English
Status: Completed
Published: 2016-10-10
Updated: 2016-12-05
Packaged: 2018-08-20 12:23:54
Rating: Explicit
Warnings: Underage
Chapters: 5
Words: 8,446
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8248847
Author URL: https://archiveofourown.org/users/Dirtykinkylove/pseuds/Dirtykinkylove
Summary: Derek has a dirty little secret: his younger brother's sixteen year old girlfriend.





	1. Chapter 1

**Author's Note:**

> I used the underage tag only because Stiles is sixteen in this story - some states/countries count that as age of consent, but I tagged it just in case.

"Hi Derek," a young female voice chirped, shaking Derek from his early morning haze. He looked up into the wicked brown eyes of his younger brother's girlfriend and watched her pink mouth bow upwards in a sly smile. She slipped around the table and settled into his lap so she faced him, her shorts covered pussy lightly pressing on his cock. There was at least three layers between them and he wished there were none, but there wasn't enough time for him to fuck her full before his wife came down the stairs.

"What're you doing here?"

"I stayed over," she responded, rocking slightly on him, obviously enjoying the rise of his erection. 

"Your dad didn't care?"

"He pulled an overnight and besides, he  _trusts_ Scott. He knows we're not having sex."

No, Stiles wasn't having sex with  _Scott_. It was Derek who'd taken her virginity over a year ago in a lust soaked night he wished he regretted but couldn't because he was addicted to her pussy. He loved licking and sucking and fucking and fingering it until she deafened him with her screams of delight. He hated wearing condoms so he paid for her birth control, which she hid in her ADD medication bottle so no one was the wiser.

Light graceful footsteps echoed into the tiled kitchen and Stiles reluctantly pulled away and went to stand at the fridge, playing the indecisive teenager to the hilt when Jennifer walked in. It was Saturday, but she was dressed to the nines, indicating she was going to the office even though it was supposed to be her day off. A few months ago the sight would've frustrated him, but now all he could think about was lying Stiles on the table and eating her out as his breakfast.

"I know, I know, honey, but it's only for a couple hours."

It was the same excuse he heard over and over until he could mouth it along with her. Jennifer was extremely dedicated and the reason why they were able to live as well as they did since his Deputy's salary was only the fraction of what she brought home. Sometimes he wondered if she was cheating on him with her boss, the handsome and debonair Deucalion, but if she was it was only fair play since the minute she backed out of their two car garage, he would be balls deep in Stiles.

"Fine," he sighed in pretend barely-disguised anger. Jennifer's mouth tightened but she refrained from commenting since they were trying to keep their disagreement hidden from Stiles. When Jennifer turned away to grab the bread from the counter, Stiles pinched her nipple through her shirt until the peak pressed obviously against the thin cotton. She was small-breasted so she didn't need to wear bras, a fact Derek appreciated because he didn't need to fumble with the clasp during their hurried encounters. He licked his lips and hollowed his cheeks the way they did when he sucked her whole breast into his mouth. A blush tinted her naturally pale face and Derek gazed at her until Jennifer crossed his eyeline, breaking their connection.

"Is Scott awake?"

Stiles recovered her poise admirably and spoke with a slightly hoarse voice. "Nah, he's still passed out. We stayed up really late playing video games."

If it were any other couple Derek would call bullshit right away, but Scott was as virginal as Stiles used to be and was so painfully honest, he wouldn't be able to hide the change in their relationship if something  _did_ happen. Not that it would as Derek continued to ensure Stiles came to him to fulfill any lusty impulses she might have. He briefly thought of the burner phone hidden in his home office filled with descriptive texts and videos exchanged between him and his young lover, how he could chart the change from timid girl to flamboyant sex kitten who enticed him into having sex in his Crown Vic while on duty. He'd nearly had a heart attack when her father, his boss, the  _sheriff_ , commented on the strange stain on the upholstery and he'd lied saying it was special sauce from his dinner the night before.

Jennifer laughed and ruffled Stiles' shoulder length hair as if she were still the skinned knee tomboy who first tumbled into their lives when she and Scott were nine instead of the gorgeous sixteen year old who sucked his cock like she was getting paid for it. Derek winced a little at the reminder of her age and the nearly fifteen year gap between them. It bothered him a little that he was so much older, but it was hard to regret it when he had her bouncing on his cock with a lithe suppleness that made his balls clench and unload in her tight snatch.

"You two are so cute together, like puppies, right Derek?"

"She's a regular doggy," he dryly retorted, his cock stiffening even further in his shorts when he remembered a few nights ago having Stiles on her hands and knees, hair wrapped around his fist as he fucked her long and hard. Stiles had passed out after two orgasms, but Derek had continued, loving the feeling of her sloppy wet pussy pulsing around him. Stiles grinned at him, clearly remembering the same memory, and leaned against the counter so he could see she wasn't wearing panties beneath the tight shorts. His mouth dried and he desperately licked his lips, wishing he was tasting her right now.

"What are you up to for today Derek?"

He shrugged. "I was planning on cleaning out the attic and doing some of the house-cleaning I've neglected this week. When Scott gets up, I'll make him help too."

Jennifer dimpled and pressed a kiss to his forehead. "I'm so lucky to have you! None of my other friends' husbands willingly clean up after themselves much less do chores they assigned themselves."

"I'm a real catch."

"Okay honey, I'll be back later. Stiles, if I don't see you, have a great week at school."

"Have fun," Stiles cheerfully returned.

Derek stayed seated until he couldn't hear Jennifer's car, then stood up so fast his chair fell backward and slammed against the floor. Stiles jumped into his arms with no hesitation, confident he would catch her; Derek didn't disappoint and groaned against her chapped lips when he felt her long legs wrap around his waist. They kissed for awhile until Derek couldn't stand the feel of his mesh athletic shorts against his cock anymore, and he lifted one hand from her buttocks to drag his shorts down. Stiles whimpered when he playfully tapped the head of his cock against her pussy lips.

"Fuck me, Der. Fuck me!"

Her demand ignited his feral side, and he pushed aside the tiny shorts and dropped Stiles down a little so his cock snugged deep inside her wet pussy. They both groaned and Derek swung her around until he could prop her against the counter, freeing him up to plunge and withdraw at a steady pace. Stiles looked drunk on pleasure, her face flushed a deep red while sweat dripped down her hairline. Derek leaned forward and started gnawing on her nipples, hating the cotton separating him from her bare flesh, but too driven to stop and undress her. Normally during sex Derek's mouth would run, grunting and groaning, swearing and calling Jennifer dirty names, but when he was inside Stiles, he couldn't speak, his whole focus narrowed down to the points of contact at their groins and chest, determined to make his lover come before him. 

His stamina proved too much for her body because her elbows gave out and she dropped on her back, body nearly bent in half as he unwrapped her legs from his waist and propped her legs on his shoulders. It changed the angle and let him go much deeper, plus he had access to her clit, which he rubbed in short fast circles even as his hips worked him back and forth. Stiles' pupils were almost completely blown, a thin rim of brown the only color left in her eyes. Derek felt a savage grin of triumph break across his face when he felt the tell-tale signs of her orgasm as her small cunt rippled around his thick length and she turned her head to bite the bone of his wrist, a spontaneous gag for her cry of pleasure.

Derek sank into her until his pubic bone rubbed against her clit and came, muscles trembling with the force of his orgasm and suddenly he understood why the French sometimes referred to it as a little death.  

"While I'm enjoying the cuddling, big guy, you're not exactly a light weight so, uh, could you move?"

Derek reluctantly raised himself off where he'd slumped on her, and pulled out, cupping his hand so none of his come could leak out of her pussy. He kneeled down and brought his mouth to her, cleaning her with his tongue, enjoying their mingled taste on his tongue. He continued until Stiles came again and pulled on his hair to warn him away from her sensitive clit. He lifted his head and wasn't surprised when she hopped off the counter and dropped down into his lap in a mirror of her position earlier so she could tangle her tongue with his and suck the come from his teeth.

He didn't know how long they remained entangled on the floor before they could hear stirring upstairs indicating Scott was awake and would soon come down. While Derek should feel guilty about moving in on his younger brother's girlfriend, all he truly felt was irritation that he couldn't spend the day buried in Stiles' cunt. Stiles hopped up with a wry smile when she looked down at her come splattered outfit, and threw a quick bye over her shoulder as she skipped out the front door. Derek knew she'd call or text or video conference him later, so he shelved his disappointment at the interruption of their morning, and set about wiping up the evidence of their affair.


	2. Chapter 2

Derek lay in his bed and watched his wife as she walked around their bedroom in a short blue negligee he'd bought for her in the beginning of their relationship. The deep sapphire color glowed against the alabaster luster of her skin and made his mouth water at the sight - or it would've had his balls not been drained an hour earlier when Stiles trapped him in the kitchen under the pretext of helping him wash dishes but instead sucked his brains out through his dick.

His young paramour enjoyed taking risks and getting skull fucked a bare thirty feet from their significant others brought out the wild side of her, and he'd had to gag her with the dishrag when he returned the favor by finger-fucking her into orgasm, pretending he'd dropped a pan when the heel of her foot smacked against the lower cabinet. Derek had never done anything wild or crazy growing up, content to leaving those types of antics to his two older sisters, so he was astonished at his capacity to not only successfully carry on a torrid affair beneath the noses of his wife and brother, but also with such an unsubtle person.

How could Jenny or Scott miss Stiles flirting with him across the table by dropping peas down her skimpy tank top which barely shielded her braless tits? Or the way she licked and sucked her spoon while staring at him from beneath those long black lashes, forcing him to remember all the times she'd spent on her knees between his thighs? She'd come to him a virgin in all ways, so he could mold and train her in how to please him utterly. Stiles didn't have preconceived notions of what girls should or shouldn't do in bed - she was curious and hyper and wanted to try everything at least once.

The first time he'd rimmed her - made her hold her asscheeks apart so he could bury his face between those surprisingly plump globes - she'd howled and writhed, but never once did she shy away or feel self conscious about being dirty there. They'd taken a shower together before hand so he could wash her body until it glowed with a healthy flush of arousal. By now Derek had fucked, sucked, licked, bitten, and reamed every glorious five foot and six inches of her lithe body in every room and against or on nearly every surface in the house. In the beginning guilt had tried to grip him because he did love Jenny, but then blood rushed to his dick and eventually the pleasure overwhelmed everything else. 

The bed he lay on and the one Jenny now slipped into, had its share of both marital and extramarital scenes, and Derek couldn't deny the special thrill of fucking Stiles on his wife's side and leaving the musky sheets for his wife to sleep on later. His dick hardened valiantly at that sly reminder that Jenny now lay in a dried wet spot made from when Stiles came so hard she squirted. Derek held his breath when Jenny snapped the side light off and turned to lay on her side.

"Horny, baby?"

He was, but not for her cunt. He wanted virgin tight that tried to keep him out so he had to coax it open like a special hothouse flower with the right touches. Stiles could get so wet that it dripped to her knees, and Derek loved lapping it up and then kissing Stiles so she could taste how delicious she was.

Derek had no choice, of course, so he reached out and brought Jenny's hand to his lap where his boxers shielded his cock. "What do you think?"

Jenny's laugh was quiet but triumphant, and Derek settled onto his back as she slid on top of him, the silkiness of her nightie brushing against the bare skin of his chest. He raised his hips and let her slide down his underwear so he could feel the slick heat of her pussy against him. He gripped her hips and allowed her to straddle him as she teasingly rubbed over his solid length.

"Do you like that, baby? Want to stick your hard dick into me?"

Derek cringed at Jenny's words and instead replaced them with a memory of Stiles saying the same thing, except she was desperate, on the edge from an hour of him holding her off for orgasm until she snapped and pushed him down, commanding him to stick his dick in her. He'd done it, fucked her and taken her hymen in one swift stroke, the slight grimace of pain the only indication she'd felt anything other relief at finally being allowed to come.

Mind full of Stiles, Derek stroked and pushed, swirled and fucked, knowing how to play Jenny's body until she cried out her satisfaction. Slumping over on him, she pressed a kiss to his ear and whispered, "I'll blow you if you want."

Derek pushed Jenny's head down until his dick was snugged into her throat before allowing his wife to set the pace. She knew him as well as he did her, so he was able to enjoy her ministrations though he wished he'd been able to save this load for Stiles' pussy.

There was always tomorrow night when the sheriff was on an overnight and Stiles was home alone.


	3. Chapter 3

Derek stifled a grunt as he swung a leg over the large branch and wriggled onto the small balcony leading to Stiles' second story window. He was fortunate she was facing the back yard and not the front, otherwise her neighbors would get an eyeful of him sneaking into her room.

Her window was half-open to let in the cool fall air, and he silently slid it all the way up and toed off his shoes before creeping to her bedside. He looked down at the sheets twisted around her barely clothed body - she'd grown used to wearing little in case he was able to get away for a midnight rendezvous - and licked his lips at the sight. Her bed faced the window and the light from the outside street lamp fell across her, barring her covers in stripes so it made her look almost other wordly. He crouched down and whistled softly, the agreed upon signal which would awaken her without giving her a heart attack. The first time he came into her room this way, she'd nearly taken a bat to his head and awakened her dad; fortunately the sheriff was used to Stiles' weirdness and didn't think anything of her explanation of a stray bat coming in the window. 

Long lashes fluttered sleepily a few times before she became fully aware of his presence. The welcoming smile warmed Derek and he eased onto her twin bed, nudging her until he was able to sprawl across her body. A small "oof" escaped her lips as he leaned his full weight on her, but she didn't protest, but instead twined her arms around his neck and leaned in close. 

"I thought you weren't able to come tonight."

Derek suppressed a tingle at the brush of her lips against his neck and scraped his chest against her unclothed breasts, relishing the shudder it sent through the slender body beneath him. Despite Stiles' smallness, her nipples were extremely sensitive and he loved playing with them anyway he could.

 "Jenny thinks I have a double shift." It was fortunate that his wife wasn't close to any of the deputies significant others because then she'd realize he went off shift an hour ago and wasn't due back until mid-morning tomorrow. She'd been spending more and more time at home since her project was completed, so Derek was forced to find creative ways to get out of the house. It was hard to make time for Stiles when she and Scott weren't dating any longer, though their split was amicable, and she had no real excuse to come to the house.  Derek was slowly get more and more desperate as his favorite sexual outlet was almost completely closed to him - though Jenny was reaping the benefits since he needed to expend his sexual energy somehow since masturbation wasn't cutting it. 

"I missed you," she whispered, shifting slightly as she slid her panties off her lean hips. Derek ground his pelvis down, letting her feel his half-hard cock through his work pants. Stiles liked being fucked when she was nude and he wasn't, another proclivity he enjoyed as well, so he made no move to disrobe.

"Unzip me and take me out."

Long thin fingers quickly unbuckled his dress belt - his duty belt already left in the car - and slowly unzipped him, the szzz loud in the otherwise silent room. Derek went commandos on days he thought he'd see Stiles, so she was able to draw him through the opening in his pants, her soft palm warm against his cock. He smiled at her contented sigh, and pushed off her so he could knee walk up her chest so he could tap her lips. Stiles grinned up at him, her lips pale against the ruddy color of his rapidly hardening dick, and delicately cat-licked the tip, swirling around the small hole in encouragement. Derek bit his lip against a groan and breathed through his nose as she sucked him deeper into the hot caverns of her small mouth, careful to tuck her tongue over her teeth.  

It had taken months of oral sex in order for Stiles to stop scraping him when she got excited, but Derek didn't mind the tutoring as any time spent buried in Stiles was a good day for him. He reached behind him and tweaked her burgeoning nipples, tugging and pulling them to the edge of pain, which in turn made her gasp. He slid in further as her throat opened up and he stayed still so she could accustom herself to breathing around his girth. When he felt her tap his thigh, he pinched her nipples hard, then let go. One day he needed to bring clips to pin her until she couldn't take the pressure any longer, and take them off at the same time he fucked long and deep. 

Derek brought himself back to the here and now, shifting his hips in small increments so his cock stayed in her mouth the entire time, while his balls gently bounced against her chin. He could feel salvia begin to pool around and drip down the sides of her mouth - the first time they ever did this, her lips cracked and bled at the corners, a sign of him doing his job well. He was greedy for her every first, for teaching her what she needed to know to please him. Derek didn't think this affair would last forever, but he would soak up each experience until Stiles tired of him and sought someone closer to her own age.

"Good girl," he praised while gently stroking her hair. "Such a good girl, letting me fuck your throat. I thought about this all day, having your mouth and cunt wrap around me."

He didn't lie to her either. He hadn't been entirely sure he could steal time enough for Stiles tonight so he'd sat in his car, grateful for his posting on the highway as it gave him privacy to play with his cock all day. He'd taken several pictures and texted them to Stiles, taking a special thrill in knowing she was looking at his dick while innocently sitting in class. Stiles never turned off the burner phone he gave her months ago, even if she did her regular phone, so he had access to her at all hours of the day and night. At one point she'd gone to the bathroom and took a shot of her gleaming folds, and another one of her fingering herself. They didn't play BDSM games, but sometimes Derek couldn't help himself from commanding his young lover, telling her how to pleasure herself for his pleasure. She'd videoed herself leaning against the stall while frigging her pretty clit, the background noise indicating she wasn't alone in the bathroom. Derek had told her to come all over her hand and lick it up, which she did, the last sight on the video of her gagging herself on glistening fingers.

Now he stared down at the Stiles' mouth contorting around him and gripped her head, fucking deep and then deeper still until he felt the constriction of her throat as she gagged. He loved that feeling and fought to keep himself still enough again for her to find her breath. Finally he pulled out and let his cock rest on her face, tracing the head across her smooth forehead and smearing precum and saliva in her hair.

Stiles scooted down a little and started suckling at his ballsack, her tongue massaging the bulge. Derek indulged her for a few minutes before moving backwards away from her talented mouth and cupped her breasts to form a shallow valley. The smallness of her breasts ensured the most he got was the peaks of her stiff nipples, but Derek enjoyed fucking between them nonetheless using spit and his wetness to create enough friction. Jenny's breasts were much fuller and he was able to actually come that way, but it was more fun to fuck Stiles' little tits because no other man had ever seen, much less touched them like this. The first time he'd caught Scott and Stiles kissing, an almost black rage had overcome him as he fought to beat the shit out of his younger brother for daring to touch what was his - fortunately for family harmony, Scott hadn't gone too far and Stiles had come to him directly afterward to let him know that.  Scott never tried to go further than holding hands or closed mouth kissing, which now they were broken up, caused Derek to smile with fond amusement because Stiles was diametrically opposite of the shy virgin Scott pictured her as. 

Derek reluctantly let go of Stiles' breasts and continued his path downward to her deep innie belly button. He loved playing with it as it looked like a small mouth opened just for his caresses. He fucked his cock tip in and out of it, grinning at Stiles' helpless giggles. He loved how unserious Stiles took sex as everything was an adventure for her. He played with his third favorite hole for awhile until Stiles whined and pleaded for more, complaining at how empty she felt. Derek soothed her oral fixation by fucking two fingers into her mouth and finally -  _finally_ \- allowed his cock to slide against her smooth wet cunt lips. Until recently, Stiles had shaved her curls down, but a week ago Derek had set her up for a Brazilian wax appointment at a salon out of town, and hadn't had the chance to touch it in person. Pictures and videos were all well and good, but nothing beat the full experience. The softness of her outer lips melted into scorching heat as he slowly sunk into her until he couldn't tell where he ended and she began. Her legs wrapped around his hips, and he used his upper body strength to hold her body against his while he thrust in and out, the roughness of his pants rubbing between her silken thighs - he liked knowing her scent and fluids would douse him so he would leave here with a small part of her still with him.

Stiles gasped and groaned, her fingers curled into his shoulders, making him glad of both the thickness of his uniform and the shortness of her nails would protect him from bruising or scratches he would have to explain to his wife. The thought of his wife knowing about him fucking Stiles, maybe even walking in on it, made his cock throb and harden further - he wanted to show off this beautiful cunt belonged to him.

"Whose cunt is this?"

"Yours! Yours!"

Her screams of capitulation echoed in the room and she convulsed as if electrified, her pussy muscles squeezing down on him until it felt like a vise had gripped him. Derek forced her down all the way and he kept her there as he fucked her though her orgasm until he couldn't withstand the pressure and creamed his young lover's cunt. He let go of Stiles and she flopped backwards, though they stayed connected at the groin, with her chest heaving. Eventually he reluctantly withdrew, his spent cock wet with their mingled release, and Stiles proved she wasn't completely asleep as she pushed him back so she could lick his cock clean.

Their lips and tongue met as Stiles shared their combined taste. Derek groaned into her mouth and pulled her fully on him, despite knowing her pussy load would drip all over him in an obvious way, leaving incriminating spots on his uniform's crotch.

"Can you stay until I fall asleep?"

Derek had made sure his car was parked a few streets away in an alley so no one would spot him. Her father wasn't coming home for another few hours and Jenny would expect him to come back after she left for work in the morning, so he had the time to sleep with Stiles and awaken her with an orgasm before she went to school tomorrow and he was forced back to his real life.

"Sleep my love," he whispered, his hand smoothing up and down her back, relishing the closeness for a little bit longer.

 

**Notes for the Chapter:**

> Hmm, somehow feels (sorta) crept into this. Damn you Derek, damn you.


	4. Chapter 4

**Notes for the Chapter:**

> A few of you requested Jennifer finds out about Stiles and Derek. I wasn't sure how it could work, but then this popped into my head.

His marriage fell apart on a Thursday evening, shortly after he got home. Derek knew this day was coming - how could it not when all of his time and attention outside of work was devoted to finding ways to fuck Stiles? Jennifer was busy, not stupid, and in a way it was a relief. They weren't the idealistic college students who were so in love with one another and their desire to conquer the world any more. In fact, Derek didn't remember being that boy for a long time and he was happier being a deputy in a small town than she was being a big fish in a little pond.

Jennifer was home early that day, an unheralded event since her workload had increased with her on track to becoming partner in her firm. Derek was tired and grumpy because he hadn't seen or touched Stiles in nearly a week because she was away on Spring Break with a few friends, the last hurrah before graduation and college. He hadn't wanted to hold her back from having fun, even if it meant she hooked up with someone else, so he'd told her to leave her phone at home. The look on her face was indecipherable, but she'd done as he requested, and now Derek sorely regretted it because he was used to constant communication with her.

"Derek, is that you?"

"Yeah," he nearly grunted in reply, slowly coming up the stairs. He'd drawn as many hours as he could this week to keep his mind busy and he was dog tired as a result. He stopped in surprise in the doorway to his room when he saw Jennifer on the bed with his laptop in her lap. They each had their own and she'd never used his in the entirety of his ownership, so he didn't password protect it. His heart rate increased when he realized all the unprotected information stored on it - Jennifer knew he masturbated to porn, but she didn't know it was homemade porn starring his little brother's ex-girlfriend and boss' kid. In the three years since his affair with Stiles started, they had pushed the boundaries further and further, until sex with Jennifer was boring and he was unable to get stiff for her unless thinking about Stiles.

"I wasn't feeling well today so I took a half day to work from home. My laptop crashed, however, so I thought I would use yours." Her voice trembled and she slowly turned the screen around so he could see his secret e-mail inbox. "Imagine my surprise when I saw this e-mail you were sent."

The e-mail was sent today from Stiles' Gmail account with the subject heading "Because You'll Get Off On It." Despite the tense situation, Derek felt his dick twitch with anticipation at Stiles' daring and imagination.

"Do you want to watch the video she attached?"

Jennifer's voice had ceased trembling and was now cold as a judge before pronouncing a life sentence. Derek numbly nodded and her long pale finger pressed play. It was obviously filmed by a smartphone as there was minute shaking associated with hand-held. The scene was a hotel room with two large beds - there was the detritus of its occupants strewn around, but Derek couldn't keep his eyes off the figures lying entwined on one bed. Stiles was half-propped up against large pillows, her thighs spread to accommodate the girl who was obviously going to town on her pussy. Derek paid monthly for Stiles to get her pubic hair waxed and he watched as the unknown cameraman zoomed in on the stranger's mouth attacking bare wet flesh.

"She said she couldn't ride dick, but there wasn't anything against the rules for her to ride a girl's tongue," the unseen woman narrated. "This slut has been eating Stiles out for hours. She always finds the unselfish ones."

Derek palmed his dick, only peripherally aware of his wife, and ached to whip it out and stroke himself to orgasm. Stiles had, as usual, protested his heavy-handed decision making in her own unique way. She knew he was possessive and jealous of her even as he struggled not to be because he had no right, and managed to get her point across while still ensuring they would both enjoy it. Derek wouldn't be able to handle her fucking another guy - at least not without him there to supervise - so she found a girl. He knew it was sexist to not be threatened by another woman, but then he also knew how much she  _loved_ dick. And if this was an avenue she wanted to explore than he would be happy to join her on this path too. He was in it for the long haul, he slowly realized, and maybe she was too. 

"Jesus Fucking Christ Derek! You're turned on by this!"

Jennifer slammed the laptop shut before he could see Stiles get off and he scowled briefly before meeting his wife's eyes. She looked...wrecked...for lack of a better word and he suddenly felt ashamed of himself, which wilted his erection.

"How long have you and her -?"

Danger. "It's not -"

"Don't act like I'm an idiot, Derek. You've been uninterested in me for  _months_! Have yyou-have the two..."

The obscene gesture made it clear what she meant.

"No, just sexting and exchanging of videos."

Not a complete lie. Stiles had recently complained that she was the only one who did them and she demanded one in exchange. Derek had thought he would be nervous or uncomfortable, but instead he was turned on, excited, enjoyed showing off his erection, his large balls, and showing her what he liked to do when he was alone. The just shy of too dry way he slowly pulled on himself, squeezing the head so pre-come dribbled out to it collected on the web between his thumb and forefinger. He liked tasting himself and knew it turned Stiles on as well, so he made sure to lick and lap at every stray drop, making obscene noises which weren't faked, much to his surprise. He spread his thighs wide and propped his legs up, having the small GoPro between them so she caught every minute of his masturbation. He looked obscene, swollen cock and bulging sack, his hand getting slipperier and slipperier with each pulse of slick he produced.  _Wish you were here baby, to suck and swallow like a good cumslut,_ he murmured, head falling back as mental slideshow of Stiles' dirtier moments aided his movements.  _I saved you a big load_ , he promised as he brought his other hand to gently roll and weigh his balls, his impending orgasm causing them to tighten against his body. The actual climax was intense and sudden like a crossbow releasing its arrow, and he'd sprayed his own chin before he covered his cockhead. After catching his breath, Derek brought the camera up so he could zoom in on the way his come gleamed on his dark-haired happy trail and then down to his still hard dick before ending the video.

"Only? Only? She's a child, Derek! How could you?"

He knew his next words wouldn't help, but he needed to get her off that track because she would really flip her gourd if she ever discovered he took Stiles' virginity a few days after her fifteenth birthday. "She's eighteen and legal, Jennifer, nor have we done anything illegal. Immoral, sure, but illegal? No."

Jennifer's face twisted and tears filled her eyes. "Why did you turn to that...that.. _girl_? Am I not enough?"

Derek sighed and stretched out on his side of the bed. He had no answer to her question - he loved Jennifer but wasn't attracted to her. Was it wrong to start an affair with a minor who dated his brother? Yes. Did he feel bad enough to stop? No. Even if Jennifer hadn't caught on, Derek knew he would've continued until Stiles herself put a stop to it. He was having too much fun and the sex was phenomenal. 

"I don't know," he bluntly replied, too tired to sugar-coat the truth. "I wasn't unhappy really; I mean, we have a good life with enough money to pay the bills, and I like living in my hometown, but...I guess I wanted something else." Hotter, dirtier, and fresh. Derek would never admit to his wife but he sometimes he got off on the adultery aspect, fucking her in places that should be sacrosanct for his marriage. He worried that he would grow tired of Stiles, but whenever he looked at girls her age, or even other women, he could find them objectively attractive, but not be physically aroused. Derek knew this was a fear Stiles had, that he would cheat on her too, because once a cheater, always a cheater right? But Derek simply didn't think it was possible, if only because he was Stiles' teacher in the sexual realm and she found nothing taboo so she was always willing to try something at least once. It was extremely arousing and ego-boosting knowing she thought he was a sex god - it was one reason why he was reluctant to share her with another guy because he worried she would find the other male better in bed.

"That's your response to the ending of our twelve year relationship - _I don't know and I liked your money_."

Fury had dried Jennifer's tears, which made Derek immensely glad because he was pants at comforting weeping women. 

"You are a goddamn liar and fucking perv! Wait until the sheriff learns what you've been up to with his daughter."

Derek sat upright at the threat and glared at his wife. Sure, he screwed their marriage (in more ways than Jennifer would ever know), but he wouldn't tolerate her destroying his job or Stiles' future.

"No, you'll leave the sheriff out of this and Stiles too. They have nothing to do with why our marriage is crumbling."

The dueling spouses scowled at one another for several fraught minutes before Jennifer looked away for a split second, signaling her submission to his insistence. "Is this why our counseling sessions stopped? Because you were too busy with...Stiles?"

"No." Yes. A year ago Jennifer had demanded they go to couples counseling to aid in repairing what she felt was a fractured relationship. Derek had no interest in disturbing the status quo because her frequent absences allowed him the freedom to fuck Stiles as much as possible, but he could only play the "crime waits for no man" card so many times, especially when she carved time out of her admittedly insanely busy work schedule for the sessions. He'd gone with her to Ms. Morrell and had participated enough to make it seem like he cared and had subtly undermined Jennifer at home so she ended up canceling the remaining sessions with the counselor herself.

"Why are you doing this? I thought we were happy and in love and..." her voice petered out.

Derek saw Jenny, the eighteen year old who sat before him in Criminal Justice class and captivated him with her passion and wit, before she slowly morphed back into Jennifer, his wife of seven years who thought a few tried and true positions were satisfactory when he had a teenager slavering for his dick 24/7. He knew he was an asshole but he never felt it more than in that moment. She couldn't hold the burden of a strained marriage on her shoulders alone and he'd done nothing to save it as it began to founder beneath the weight of his lies and her dedication to work. Before he'd ever touched Stiles, before they exchanged longing glances, Derek had loved his wife and had thought they were in a good place despite a few key differences. When their differences began to overwhelm their similarities, Derek withdrawn emotionally and eventually physically too. 

"Jenny, be honest with me. When we first got married, we were happy yes, but when I convinced you to move to Beacon Hills to be closer to my family, things changed between us. I would never have been tempted by Stiles if we were in a good place emotionally and I'm sorry for that."

Jennifer considered him for a minute. "Derek James Hale, I want you to look me in the eye and swear to me that you've never had sex with Stiles and the only thing you two have done is exchange sexually charged texts and e-mails."

He was able to look into her big brown eyes and lie successfully that his dick never fucked into Stiles' slick wet cunt, that his mouth never suckled her small titties, or his hands hadn't bent and twisted the teen into perfect forms for him to play with. Derek was almost scared by his ability to get past his wife's well-honed bullshit meter, but then he'd successfully carried on a three year affair beneath her nose, even going so far as to fuck his mistress on the floor in the same room where his wife was sleeping without her being aware of it. Despite the situation, Derek's dick twitched at memories of that night - smuggling Stiles into the hotel room and laying her back on the blankets he'd put down, gagging her with her own panties as he used every trick in the book to make her cum without waking Jennifer. 

"Okay, okay, I believe you. I still hate you for what you've done to us, but at least you haven't crossed that line."

Not only had he crossed that line, but he'd set it on fire and fucked Stiles in its ashes.

"What do you want to do?" The frown on his face and the sadness in his heart weren't feigned as he really was sorry for how this all played out, but a larger part of him felt relief and wonder.

"I think you need to pack your bags and stay at Laura's for a while until I draw up divorce papers."

"What about Scott?"

"He can stay here if he wants, but he's mostly with Allison anyway at her apartment, so I'm sure he wouldn't be heart-broken if he got to move in with his girlfriend a few months earlier than they planned." 

Derek fought the instinctive need to roll his eyes because Jennifer might take it as criticism of her instead of being directed at Scott and his "true lurve" Allison Argent. The two of them were sickening sweet and if Disney Princess was what Scott desired, it was a wonder he ever dated Stiles in the first place (though he knew from Stiles' confession she had dated Scott to get access to him, though she never thought she would _actually_ _get_ Derek).

"If that's what you feel is best."

"I do," she said. "I'm going to get out of here for a few hours while you -" she waved her hand towards the closet and didn't finish her sentence. Tears were beginning to fill her eyes again and Jennifer rushed from the room towards the ensuite bathroom. Derek stayed motionless on the bed and she darted out a few minutes later. He listened to her go to the garage and back her car out. Once the whine of the garage closing stopped echoing through the house, Derek shucked his clothes off, dick hard again, and reached for his laptop.

It wouldn't take him long to pack, so he had more than enough time to watch Stiles' video.


	5. Chapter 5

**Summary for the Chapter:**

> The aftermath.

Derek took his mouth off Stiles' pussy when her hands started pushing him  _away_ instead of dragging him closer. She lay in a comfortable sprawl on his bed, her naked body gleaming with sweat. Derek felt pride and bone deep contentment at knowing he'd pleased her so well.

"Damn Derek, you tryna kill me?"

He dropped his head to one pale thigh and laughed at her, affection warming his heart. He'd missed her so much when she was away at college and lived for the weekends she was able to drive back or the breaks when she could stay for more than a few hours. Derek couldn't deny the thrill of fucking her while she was underaged - they still roleplayed the situation sometimes - but he enjoyed being her boyfriend more. They had waited until she was almost through her undergraduate program before publicly dating, as the gap in their ages wasn't as bad when she was in her early twenties. Jennifer had left Beacon Hills by then and Scott was married to his high school sweetheart (the girl he dated after breaking up with Stiles), so they'd only worried about the sheriff's reaction.

John had merely sighed and shook his head, saying he'd braced himself for years waiting on their announcement. At first Derek had thought the sheriff knew about their illicit affair, but that fear was laid to rest when the sheriff had gently teased his daughter about her obvious crush on Derek, and the illuminating happiness when she'd heard the news of his divorce.  They'd long since come up with a story about how they got together - they'd run into each other again during one of Stiles' visits and Stiles had bugged him into an e-mail correspondence - which had John sighing again over Stiles' stalker tendencies, and the matter was laid to rest. 

"-something to tell you."

Derek snapped back to the present and tried to look like he'd been listening, but Stiles had over a decade's worth of knowledge about Derek plus a girlfriend's innate intuition when her mate wasn't paying attention so he soon caved and meekly asked her to repeat her comment.

Stiles rolled her eyes but repeated her words. "So, I, um, have something to tell you."

"What?"

"Remember Mia?"

How could he forget her? She was the girl Stiles met and fucked over Spring Break years ago. He still had the video of them fucking that precipitated the end of his marriage, and which he beat off to when she was gone and he was horny. Despite her fears - one of the worst arguments in their relationship was the result of her jealousy over a new pretty female deputy in the department before they went public - Derek was never tempted to stray despite the strain of keeping a long distance relationship alive. He had found his forever in a fifteen year old girl and his heart hadn't wavered since. While he sometimes regretted the circumstances of their  _real_ relationship start, also how much he hurt Jennifer in the process, he would never regret the chance he was given to have her now.

"Yes," he husked in response. "Her lingual abilities still astound me."

Stiles slap upside the head was fond. "She e-mailed me the other day and said she was going to be near Stanford, and wanted to meet up."

Derek frowned. He never begrudged her the Spring Break hookup because he had essentially pushed her into it due to his own insecurities, and he enjoyed the video or hearing Stiles recount it while they fucked, but their monogamy was part and parcel of how they made it through the rough bumps. At first he'd tried to convince Stiles to have an open relationship - at least on her part since he'd already lived and fucked his way through college - but the epic showdown that followed had scared him off suggesting it for life.

Now was she saying what he thought she was saying?

"You want to fuck her again?"

His voice wasn't even and steady but ringing with the fury starting to gather in his chest. He'd grown used to being able to refer to Stiles as  _his_ , and part of being  _his_ meant no one else got to hear the funny hitch in her breath right before she came, or know she still slept with the stuffed rabbit her mom gave her when she was five, or knew exactly how many moles were scattered across her body (12).

"What?"

Derek jackknifed upright and glared down at her. "You're mine, Prudence Hortensia Stilinski, and you don't have the right to fuck anyone else." Her amber eyes widened at the use of her real and full name. He ignored the silent outrage as he was on a roll now. "You're  _mine_ to fuck, to love, and no fiancee of mine is gonna step out on me. Maybe I deserve it, given...everything...but..." his voice petered out at the astonishment clear on Stiles' face. 

"Fiancee?"

Derek closed his eyes and silently cursed. He'd planned his proposal down to the very minute - sunset, her favorite time of day - and now his temper had ruined it.

"Yeah," he confirmed quietly. "I wanted it to be special."

Her disbelieving "You want to marry  _me_?" had Derek opening his eyes in confusion.

"No, I want to marry Mrs. Martin's gardner. Of course  _you_."

"But you always change the subject whenever marriage is brought up."

"Well, yeah, because I was waiting until you were done with your Ph.D and came back home."

"That's in two years!"

"Yeah, so?"

"I thought you would never marry me, or would  _want_ to get married again."

Because of Jennifer.

Because of their affair.

Derek dropped to her side and urged her into his embrace, his outrage over Mia completely forgotten in the need to explain himself.

"Stiles, we've been together for nearly eight years, and a good portion of that time was spent under the radar because of your age, because I was married, a whole host of problems due to our inauspicious beginnings, but that never meant I didn't plan on spending the rest of whatever days I'm granted on earth with you." He gently stroked her hair and kissed her temple. "I want you now as a hot young woman and I want to see how you'll change and age into the crotchety old woman you're not so secretly beneath that hot exterior."

Stiles huffed a nearly silently laugh and curled deeper into his arms, hiding her face against his chest.

"Mia never e-mailed me," she mumbled-confessed. "I just said that because it drives me crazy how jealous I get over you, and you never seem to for me."

Derek winced at that. He wasn't jealous of Stiles because he knew her loyal and steadfast heart would never let her betray someone she gave her word to. He had hoped she would have the same knowledge of him, but realized the age difference and his previous marriage worked against him. They'd gone to counseling - together and separately -  after the Deputy Parrish debacle, and he's apparently wrongly assumed all their issues were revealed and resolved.

 "I want to marry you. You want to marry me?"

"Yes."

"And this isn't the engagement story I hoped we'd tell."

But it was part of their crookedly stitched pattern, and ultimately that's all that truly mattered.

**Notes for the Chapter:**

> So the sexy became soppy feelings instead. Blame Derek. I may write up the side memories of their relationship, but I can't predict when.


End file.
